In a reaction using a compound having hydroxy group(s), particularly in the synthesis of sugar chain, sugar and its derivatives to be used for the reaction have many hydroxy groups which are undesirable in the formation of desired linkage. Therefore, it is required that such hydroxy groups be protected by protecting groups to prevent the participation in the reaction system for sugar chain extension. On the other hand, it is also necessary to successively eliminate protecting groups of certain hydroxy groups involved in the sugar chain linkage, so that they can function as acceptors. That is, in a sugar chain extension synthesis, for example, particular protecting groups are bound to specific hydroxy groups such that they can be removed where necessary, and a procedure of selective cleavage and linkage of new sugars to be added is repeated. These protecting groups are essentially required to allow selective elimination as necessary and to be stable under various conditions employed for the formation of glycoside linkage and cleavage of other protecting groups. In automatic synthesis such as solid phase synthesis, among others, the protecting group to be used needs to have superior resistance to acid, since Lewis acids are used for glycosidation, and the protecting group is continuously exposed to acidic environments.
In automatic synthesis of sugar chain, moreover, elimination of protecting groups needs to be done under relatively mild conditions of temperature and pH.
Conventional hydroxy-protecting groups, such as a p-methoxybenzyl group and a p-azidobenzyl group, permit elimination of protecting group under relatively mild conditions, and pose no problem in this regard. However, they are poor in resistance to acid, and efficient synthesis of sugar chain, particularly that of sugar chain having a side chain, using these protecting groups has been extremely difficult.
Despite various attempts so far made to develop a hydroxy-protecting group in view of such situation, a satisfactory hydroxy-protecting group has not been developed yet, which is superior in resistance to acid and which can be eliminated under mild conditions.
It is therefore an object of the present invention to provide novel derivatives capable of introducing hydroxy-protecting group(s) into compounds having hydroxy group(s), which can be used for conventional hydroxy group protection, conventional liquid phase synthesis of sugar chain and continuous sugar chain solid phase synthesis using automatic synthesis apparatuses.
It is also an object of the present invention to provide a sugar compound protected using said derivatives and a method for protection of hydroxy group(s) using said derivatives.